Bolt construction



March 30 1926.

W. A. DUNLAP BOLT CONSTRUCTION Filed August 8 5R%" I $64M jNVENTOR M de A TTQRNEYS.

Patented Mar. 30, 1926.

UNITED 'sTArEs WILLIAM A. DUNLAP, OF PITTSBURGH, PENNSYLVANIA.

130m CONSTRUCTION.

Application filed August a, 1924. Serial No. 730,953.

To all whom it may concern:

Be it known that I, WILLIAM A. DUNLAP, a citizen of the United States residing at Pittsburgh, in the county of Allegheny. and State of Pennsylvania, have invented certain new and useful Improvements in Bolt Construction, of which the following is a specification. v I

My invention consists of an improvement in hollow bolt construction. Ithas for its object to provide a supporting bolt, particularly adapted to use in connection with an upper crossbar and a lower supporting element, as an outlet box or plate, etc. In the use of such boxes, which are usually mounted against the ceiling of a room for distribution of electrical circuits, the box is suspended byivarious means, and frequently from the usual lathing forming a portion of the ceiling. p

My invention has in view to provide a bolt of cheap and simple construction and manufacture, having an upper transverse slot for connection with a supporting bar, adapted to rest upon the upper surfaces of the lathing and to extend by its lower portion through the upper wall of the outlet box, for connection therewith by a clamping nut.

The invention is illustrated in the accompanying drawings, in which Flg. 1 is a sectional View through a portion of a ceiling, showing the invention as used;

Fig. 2 is a transverse view thereof, on the line 11-11 of Fig. 1, the outlet box and clamping nut being omitted;

Fig. 3 is a composite view showing the blank and also an end view of the complete bolt in dotted lines, as formed therefrom;

Fig. 4 is a sectional view showing the operation of forming the blank between the forming dies;

Fig. 5 is a similar sectional view on the line V-V of Fig. 4, showing the mandrel in elevation;

Fig. 6 is a view showing the formed blank after chasing the threads thereon, as held by the clamping mechanism;

Fig. 7 is a plan view showing a modified form of blank;

Fig. 8 is a longitudinal sectional view of a bolt made therefrom;

Fig. 9 is a cross section on the line IX-IX of Fig. 8.

Referring to Figs. 1 and 2, the outlet box 2, which is usually of pressed sheet metal, is suspended upwardly against the: under surface of the ceiling by means of a.

bolt extending through a central hole in ts upper wall. For the purpose of ensurmg a good bearing over several of the lathing 8 of the ceiling, I utilize a bar 4, whlch rests edgewise thereon, as shown, for

distribution of the strains. The bolt 5 of the present invention extends downwardly through the hole of box 2 and issecured thereto by one or, more ordinary nuts 6..

The upper portion of the bolt5 is slotted as at 7, for embracing connection with bar lby means of a cotter pm orsinnlar device 8, extending through registering-holes in lindrical bolt unit, as shown. For the pur-;

pose of providing a rounded end 9, formed of the middle section of blank a, and facilitating the curvature to shape the device throughsuitable dies,lthe. blank. is nar rowed at each side of its middle, as indi cated at b'b;

In the same way, toprovide clearance for slots 7, the opposite ends of the blank are narrowed inwardly toward a terminal shoulder, as indicated at c, SllillClBIlt metal being removed so that, when the edges of the blank are brought together in the dies, a definite open ended slot 7 at opposite locations of the upper portion of the bolt will be provided for clearance of the bar 4. The blank a as thus made is forced by a mandrel 10 through and between the halfround forming dies 11-11, as indicated in Fig. 4:, which operation rounds the end 9 upon the similarly rounded end of the mandrel 10, and brings the opposite edges of the middle portion of the blank closely against each other, as indicated at 12.

For the purpose of definitely forming the slot 7 at the upper portion of the bolt, mandrel 10 is provided with oppositely located wings 1313, of a width conforming to that of theresulting slot 7 and of the total clearance of the shouldered offset portionscc of the blank. When the blank is thrust inwardly between the dies 11 of mandrel will be formed into shape, as shown in Figs. 4 and 5, in a single operation, leaving the end 9 of the bolt rounded and smooth, because of the integral cross section, while the edges meeting closely along the line 12 provide a smooth unobstructed periphery throughout the whole length of the bolt.

After being thus formed, the blank is then mounted upon a second mandrel 14: having a pair of wings similar to wings 13 engaging slots? and with a central pushing rod or barf15 for ejecting the finally threaded and finished bolt, as indicated in Fig.0. The blank is clamped upon mandrel 14L and fixedly held in position for chasing the threads by well known chuck-head clamping mechanism 10-17, the chasing of the threads being quickly accomplished by'a turret machine, in the manner'well understood in the The blank a is also punched out as at 18 at each end,'in oval form, providing for cotter pin holes when the blank is formed into a cylinder.

An alternative form of the, bolt is shown in Figs. 7 ,8 and 9. In such construction, the blank 0:, an is of'the same general shape as described, except that its ends are of full width, and'are provided with the closed end slots 7*. The slots are punched out by suit-' able dies, leaving the punch blank, however, in the whole, severed but not removed, in the manner commonly practiced in providing the holes in the sides of the outlet box and in other similar devices. Thereafter, the blank is formed into the hollow cylindrical bolt shape in the manner already described, the slots 7 are cleared of their waste punch plugs, and the device is then ready for threading and insertion of the supporting bar 4 through the slots.

The advantage of retaining the punched out pieces in the blank during shaping in the dies is that they act like the mandrel wings 13 in bracing the blank to retain the full desired width of the slots in the final article. The closed slot construction avoids the necessity of the cotter pin 8 and also provides for longitudinal adjustment on the bar 4, if desired. i i

The resulting bolt 5 or 5 -as thus made and threaded comparatively light, and ofainple strl-ength for its intended use. It involves comparatively limited amount of machine work, and is inexpensive to manufacture, 'while extremely durable and efficient when used in the manner shown. Whilefit is particularly adapted to suspension of outlet or circuit boxes, it 'will' be readily understood that the bolt may be also; used for various other 'pur'poses;'that it may be madeof any' desired length or diameter,

and variously changed or modified by the skilled mechanic in other respects, within.

the scope of the following claim.

"WhatI claim is: A bolt of the kind described formed of a sheet metal blank bent upon itself atthe middle to form an integral rounded-end cylind'e'rwith the edges of the blank in contact beyond the rounded end and provided with threads for a portion of its length and 0p posite clearance slots for a supporting bar at its other end.

In testimony whereof I affix my signature: I

WILLIAM A. DUNLAP. 

